Subgap Density-of-States-Based Amorphous Oxide Thin Film Transistor Simulator (DeAOTS)

The amorphous oxide thin-film transistor (TFT)-oriented simulator [subgap Density of states (DOS)-based Amorphous Oxide TFT Simulator (DeAOTS)] is proposed, implemented, and demonstrated for amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs. It only consists of parameters having their physical meanings and is supplied with concrete techniques for parameter extraction. Among the physical parameters, the acceptor-like DOS
gA
(
E
) was experimentally extracted using the multifrequency
C
-
V
technique, whereas the donor-like DOS
gD
(
E
) and the doping concentration
ND
were extracted using numerical iterations. The simulation result reproduces the DOS and thin-film-thickness-dependence of dc
I
-
V
characteristics very well. Compared with the previously reported a-Si TFT models, the proposed DeAOTS model not only reflects the strong
V
_GS
dependence of the effective mobility (μ
_eff
) but also clarifies the relations between process-controlled DOS parameters and dc
I
-
V
characteristics based on experimentally extracted DOS parameters. Also, it sufficiently takes into account the peculiar situation of amorphous oxide TFTs where the free-carrier charge can be larger than the localized one out of the total induced charge. Moreover, it reproduces the measured electrical characteristics within the wide range of
V
_GS
/
V
_DS
with a single equation, not distinguishing the operation regions such as the subthreshold, linear, and saturation regimes.